Eleven patients with free vascularized fibula graft transplants to the upper extremity were studied for donor-side morbidity effects. Based on their surgical follow-up times, the patients were divided into either group 1 (5 +/- 2 months) or group 2 (21 +/- 8 months) to examine the effects of surgical trauma more closely. Gait evaluation was performed using two walkways containing different ground conditions. Knee and ankle-foot motion was measured using a three-dimensional electrogoniometer. Basic temporodistance factors and ground reactions were obtained from foot switches, instrumented floor mats, and a force plate. A modified Cybex II isokinetic dynamometer was used to quantitate ankle-foot strengths. Moderate knee and ankle-foot motion changes were seen while walking on the level, sideslope, and ramp in patients evaluated less than 10 months after their surgical procedure. Minimal joint motion effects were discovered in patients with follow-up times longer than 10 months. Muscle strengths were significantly impaired in both groups, especially foot inversion and eversion. An inverse relationship existed between the length of resected fibula and ankle evertor muscle strength. Donor side morbidity does not appear to be caused by surgical soft-tissue trauma exclusively. These patients need to be studied for several more years to determine the long-term functional effects of free vascularized fibular graft transfer.